Tensioning assembly

ABSTRACT

A tensioning assembly for connecting an outer component to a shaft. The tension assembly includes a double conical ring with a cylindrical circumferential surface and two oppositely inclined conical surfaces, and also includes two further conical clamping rings with each conical clamping ring having a conical circumferential surface which interacts with one of the conical surfaces of the double conical ring. Axial tensioning screws and axial forcing screws are uniformly distributed over the circumference of a pitch circle, such that the forcing screws are located at the same spacings and instead of the tensioning screws. At one location, a tensioning screw is provided outside the uniform spacings in order to ensure the correct alignment of the conical rings on the double conical ring in the circumferential direction.

BACKGROUND OF THE INVENTION

The invention relates to a tensioning assembly for connecting an outercomponent having a cylindrical aperture to an inner component having acylindrical outer surface and arranged concentrically in the aperture.

A first tensioning assembly of this type is known from German patent 2329 940 A 1. Each individual conical ring disclosed therein has a conicalsurface and a cylindrical circumferential surface, the cylindricalcircumferential surface resting directly against the oppositecircumferential surface of the hub or shaft. A tensioning assembly inaccordance with German patent 24 58 229 A 1, discloses conical ringshaving two conical circumferential surfaces wherein each conical ring isassigned a further conical ring which has a conical surface and acircumferential surface. The conical rings which interact with thetensioning screws thus exert their radial force on the adjacentcylindrical circumferential surface of the shaft or of the hub via thefurther conical rings.

The common feature of the two embodiments is that the conical rings andthe circumferential webs of the double conical rings have the bores forthe tensioning screws and the forcing screws on a common pitch circleand at the same spacings. As a consequence, at some locations on thecircumference bores for forcing screws are arranged in the positions inwhich tensioning screws would normally be located. This designconsiderably simplifies the production on a drilling unit withcorresponding dividing apparatus.

The uniform spacings, while providing advantages in terms of production,nevertheless involve problems regarding the correct installation of thefront conical ring, the front conical ring being directed toward thecaps of the tensioning screws. The problem of misalignment can occurwhether assembly takes place at the factory or on site, e.g. whenfastening belt-drive drums for conveying belts in mining or the like.Incorrect installation can easily occur because it is not easy to see,from the front, whether the conical ring is in the correct angularposition with respect to the double conical ring. When in the correctposition, the various types of bores coincide precisely. In the event ofcareless installation, sometimes the threaded bores in the front conicalring, (the front conical ring being directed toward the caps of thetensioning screws), and the threaded bores for releasing the frontconical ring from the double conical ring, are located opposite and inalignment with threaded bores in the circumferential web of the doubleconical ring which are provided for the release of the conical ringdirected away from the caps of the tensioning screws. Since the numbersof forcing screws for releasing the front conical ring and the rearconical ring are equal and the forcing screws are distributed uniformlyover the circumference, all the threaded bores in the front conical ringmay be located opposite the threaded bores in the circumferential web.No indication of this misalignment is given by insertion of thetensioning screws.

After the relative positions of the rings have been set, the forcingscrews are screwed into the threaded bores of the front conical ring andcome into contact with the threaded bores in the circumferential web. Asa result, it is more difficult to force off the front conical ringbecause there is no real abutment to effect the necessary leverage. Inaddition, the threaded bores in the circumferential web are destroyedsuch that, in some circumstances, it is no longer possible to force offthe rear conical ring and consequently the entire conical tensioningassembly can no longer be released.

It may be a number of years before this situation arises, when releaseof the tensioning assembly is already made difficult enough by corrosionand dirt. Accordingly, when such a case does occur, the damage isconsiderable.

SUMMARY OF THE INVENTION

The object of the invention is to avoid incorrect angular positioningduring installation of the conical rings of a tensioning assembly.

This object is achieved according to the invention by offsetting onetensioning screw bore in the circumferential direction. This simpleoffsetting measure ensures that one tensioning screw bore does not fitin with the spacings. Therefore, there is only one angular position ofthe front conical ring with respect to the double conical ring in whichall the tensioning screws can be screwed in during installation. If atensioning screw cannot be screwed in, this indicates that the angularpositioning is incorrect. If a tensioning screw intended for coincidingwith the uniform spacings is aligned with the offset through-bore in thecircumferential web, none of the other screws is aligned with anaperture. In this manner, an obvious indicator provides a positivecontrol for the correct positioning of the front conical ring withrespect to the circumferential web.

DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is illustrated in the drawings,in which:

FIG. 1 shows a side view of a conical tensioning arrangement, thetensioning assembly being reproduced in a longitudinal section, runningthrough the axis, along line I--I in FIG. 2;

FIG. 2 shows a partial view according to FIG. 1 from the left;

FIGS. 3 to 5 show partial cross sections through the tensioning assemblyalong lines III--III and IV--IV in FIG. 2 and a corresponding partialcross section in the case of incorrect installation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Shown in FIG. 1 and designated as a whole by 10 is a tensioning assemblyfor connecting a shaft 1, with an axis A, to an outer component 2 in theform of for example a gear wheel, a drive wheel, a belt-drive drum or ahub in general. The cylindrical outer circumference 3 of the shaft 1 hasa smaller diameter than the cylindrical inner circumference 4 of theouter component 2. The tensioning assembly 10 is arranged in theinterspace.

In the exemplary embodiment, the tensioning assembly 10 comprises adouble conical ring 20 with a cylindrical outer circumferential surface21 and two inner conical circumferential surfaces 22, 23 which areinclined in opposite directions to one another such that the largestwall thickness, as seen in the axial direction, is located in the centerof the double conical ring 20. In the center, that is between theconical surfaces 22, 23, the double conical ring 20 has acircumferential web 24 projecting radially inward from the doubleconical ring 20. The circumferential web 24 rests, by means of itscylindrical inner circumferential surface 25, against the othercircumferential surface 3 of the shaft 1, such that the circumferentialweb can assume centering tasks.

The double conical ring 20 is assigned two individual conical rings 30and 40, each of which, in the exemplary embodiment, has a cylindricalinner circumferential surface 31 and 41, respectively, and a conicalouter circumferential surface 32 and 42, respectively. The conical outercircumferential surfaces 32 and 42 interact with the conical innercircumferential surfaces 22 and 23. The conical surfaces 22, 42 and 23,43 have cone angles in the self-locking region and rest against oneanother, while the inner end sides 33, 43 of the conical rings 30, 40are still at an axial distance from the circumferential web 24.

The tensioning assembly 10 is braced by means of axial tensioning screws5 having caps 6. The axial tensioning screws are distributed uniformlyaround the circumference corresponding to appropriate apertures.According to FIG. 1, the axial tensioning screws are threaded throughthrough-bores 36 in the front conical ring 30 and through-bores 26 inthe circumferential web 24 and engage threaded bores 46 in the rearconical ring 40 (the rear conical ring being directed away from the caps6).

The circumferential web 24 projects radially inward from the conicalsurfaces 22, 23. The double conical ring 20 is rather thin-walled incomparison to the radial extent of the circumferential web 24. In theexemplary embodiment, the radial extent of the circumferential web 24 isapproximately three times the largest wall thickness in the region ofthe conical surfaces 22, 23. The region of the radial projections of thecircumferential web 24 is taken up by the conical rings 30, 40 and thetensioning screws 5 also run into this region. The conical rings 30, 40are thus relatively thick-walled in the radial direction such that thebores for the tensioning screws 5 and, in particular, the caps 6 thereofcan be accommodated in the radial extent of said conical rings 30, 40.As a result of their thick walls, the conical rings 30, 40 are fairlystable and, without any special measures being provided, resistdeformation such that the deformation of the conical rings requires avery high proportion of the tensioning force of the screws 5. Thisdeformation force does not contribute to the clamping force. In order toreduce the resistance to deformation and to consequently increase theproportion of the tensioning force of the screws 5 contributing to theclamping action, the conical rings are provided, in the exemplaryembodiment, with a slit 9 through the conical rings in a plane passingthrough the axis.

When the tensioning screws 5 are tightened, the conical rings 30, 40 aredrawn axially against one another. The conical surfaces 32, 42 of theconical rings 30, 40 slide on the conical surfaces 23, 22 and widen thedouble conical ring 20 radially such that the outer component 2 isclamped on the shaft 1.

Since the conical surfaces 22, 42 and 23, 32 are located in theself-locking region, the axial tensioning force of the tensioning screws5 is converted into radial clamping force with relatively highefficiency. However, because the assembly is self-locking, oncetightened, the tensioning assembly cannot be released again of its ownaccord; rather, special measures are required for release purposes. Therelease measures are explained with reference to FIGS. 2 to 5.

Substantially all the tensioning screws 5 are located on a common pitchcircle 7 at uniform spacings. The uniform spacing is indicated in FIG. 2by the angle 8 between each two adjacent bore locations in thecircumferential direction. At some locations, e.g. three uniformlydistributed locations, there are no tensioning screws 5 at the relevantspacing positions; rather, prepared configurations for forcing screwsare provided.

Such a forcing screw configuration is shown in FIG. 3. At this location,the conical ring 30 has a through-bore 36, the circumferential web 24has a threaded bore 27, and the conical ring 40 has a bore-free location44. According to FIG. 3, it is possible to screw in a screw, e.g. anunscrewed tensioning screw 5, at this location and to force off theconical ring 40 away from the double conical ring 20.

Another forcing-off arrangement, which is situated at anothercircumferential location, is represented in FIG. 4. In this case, theconical ring 30 has a threaded bore 37 and the circumferential web 24has a bore-free location 28. The configuration of the other conical ring40 at this location is immaterial. By screwing a screw 5 into thethreaded bore 37, the conical ring 30 is forced away, according to FIG.4, from the double conical ring 20.

In this manner, the two conical rings 30, 40 can be reliably releasedfrom the double conical ring 20 independently of one another.

During the installation of the tensioning assembly 10, it is difficultto see, from the front, the type of configuration of the circumferentialweb 24 behind the respective bore of the conical ring 30. In unfavorablesituations, e.g., those situations not in accordance with the presentinvention, the conical ring 30 might be assembled with the doubleconical ring 20 in such an angular position that the threaded bores 37and 27 come to coincide with one another as shown in FIG. 5. In thiscase, the tensioning screws 5 can be readily screwed in and tightened.Bracing with incorrect relative positioning of the conical ring 30 andthe double conical ring 20 can thus take place unnoticed. If, then,after some time has passed, a screw 5 is screwed into the threaded bore37 from the front for release purposes, it comes into contact with thethreaded bore 27, and, under the necessary large forces, the screw willwork its way into the thread of the threaded bore 27 to some extent.Even if it is still possible to draw off the conical ring 30 away fromthe double conical ring 20, the thread of the threaded bore 27 is stillruined such that it is no longer possible to screw a screw into thethreaded bore 27 in order to release the conical ring 40.

In order to prevent this situation and in accordance with thisinvention, a tensioning screw 5" with the associated bores is, at onelocation, offset in the circumferential direction, by a small angle 15from the normal spacings. Therefore where the tensioning screw wouldhave taken up the position 5' indicated by dashed lines in FIG. 2 itnow, instead, is positioned at 5". There is then only a single relativeangular position of the conical ring 30, in the circumferentialdirection, with respect to the double conical ring 20, in which all thetensioning screws 5 can be screwed in. This position is, of course,selected so as to provide the forcing-off configurations according toFIGS. 3 and 4, and not according to FIG. 5. It is then impermissible forthe situation of FIG. 5 to arise. If a tensioning screw 5 or all thetensioning screws 5 but one cannot be screwed in, then this is adefinitive indication that the angular positioning of the conical ring30 is incorrect. In the exemplary embodiment, the offset tensioningscrew 5" is located beside the slit 9. In this manner, it is easy tofind the location situated outside the spacings.

I claim:
 1. A tensioning assembly for connecting an outer component toan inner component comprising:(a) a double conical ring havingconcentric first and second peripheral surfaces, the first surface beingcylindrical and adapted for engagement with a surface of one of the twocomponents, the second surface having two oppositely inclined conicalsurfaces arranged such that the double conical ring has a maximum wallthickness in its midportion; (b) first and second conical clampingrings, each conical clamping ring having a conical circumferentialsurface for engaging one of the two conical surfaces of the secondsurface of the double conical ring, each conical clamping ring furtherhaving a cylindrical surface adapted for engagement with a surface ofthe other of the two components; (c) a circumferential web projectingradially from the second surface of the double conical ring, wherein thecircumferential web extends between the first and second conicalclamping rings; (d) axial tensioning screws for axially advancing thefirst and second conical rings toward the circumferential web, eachaxial tensioning screw having a cap end; (e) axial forcing screws foraxially separating the first and second conical rings from thecircumferential web; (f) aperture sites located at uniform intervalsaround the first and second conical rings and the circumferential web;and (g) an offset aperture for aligning the first and second conicalrings and the circumferential web, wherein the offset aperture islocated along the circumference of the rings and web at a location otherthan the aperture sites; wherein the forcing and tensioning screws aredistributed such that some tensioning screws are provided at someaperture sites where the first conical ring has a through-bore, thecircumferential web has a through-bore and the second conical ring has athreaded-bore, such that some forcing screws are provided at someaperture sites where the first conical ring has a through-bore, thecircumferential web has a threaded-bore and the second conical ring hasno bore, and such that other forcing screws are further provided at someaperture sites where the first conical ring has a threaded-bore and thecircumferential web has no bore; wherein one tensioning screw isprovided at the offset aperture where the first conical ring has athrough-bore, the circumferential web has a through-bore, and the secondconical ring has a threaded-bore; and wherein only one relative positionamong the first and second conical rings and the circumferential webprovides this alignment among the aperture sites and the offset apertureof the conical rings and the circumferential web.
 2. The tensioningassembly of claim 1 wherein the first and second conical rings comprisea plurality of rings.
 3. The tensioning assembly of claim 1 wherein eachof the first and second conical rings has a slit for decreasingresistance to deformation.
 4. The tensioning assembly of claim 1 whereinthe aperture sites are located on a common radius circle around thecircumference of the conical rings and circumferential web.